Technical Field of the Invention
The present invention relates, generally, to the lubrication of bearings and internal components through the use of oil mist.
Description of the Prior Art
It is widely agreed within the rotating equipment market that oil mist lubrication of bearings offers many advantages over standard oil sump lubrication. The oil intended for lubrication is atomized prior to being introduced into the bearing chamber and contacts the surface of the bearings to create an oil film. Due to the bearings not running through the oil sump, such improvements can be seen in the areas of power consumption, oil consumption, the amount of heat generated and the amount of wear on the rotating and stationary components.
Oil mist as a form of lubrication has been in existence for many years. It typically exists in the form of large scale centralized systems that distribute mist to a large number of bearing chambers. Although the use of oil mist has shown to significantly improve the general running of bearing chambers it does have a number of restrictions which have meant that it is still not widely used:                Due to the centralized nature of the oil misting unit, all of the attached equipment must be within a 500-meter radius;        Any damage that occurs to the unit has the potential to affect all the attached machinery and thus can be extremely costly in the event of a failure;        High initial and installation costs deem it unfeasible on smaller or older plants;        The physical space required is large, with a central system and hard-piping to transfer the oil mist;        It is a compromised solution, unable to meet the oil mist requirements for pumps as only one specific oil can be selected, other pumps needing different oils would have to use conventional lubrication methods;        In the event that equipment is moved or relocated, little flexibility is offered;        Distribution pipe work, from a centralized system must be inclined from the source, so to allow coalesced oil mist to run back to the source under gravity.        
The prior art includes lubrication systems, e.g., P.C.T. Application Publication No. WO 2007/028935, that have shown that by using a singular unit per housing many advantages can be achieved. The item has lower initial and installation costs, specific oil can be used with individual pieces of equipment and there is low level of maintenance.
One problem with this type of single-point lubrication system, however, is that it generates a large amount of positive pressure within the housing, due to the method of drawing oil from the chamber up to the misting unit above. This is not only an inefficient use of compressed/dried air, but also requires that the bearing housing has costly positive bearing seals installed to contain the oil mist.
Another problem is that oil mist will escape to atmosphere if the venting system only uses the positive pressure created by the mister to force it through a filter.
In addition, this kind of system can suffer from the following effects:                Trapped air within the oil suction tube can occur if a drop in pressure occurs, causing inconsistent misting results;        Blockages or restrictions in the vertical line can cause the supply of oil to be cut off completely, resulting in no mist generation;        Mist is input into the central bearing chamber contacting only some of the bearing race.        